He left office in 1980. Something else really important happening in 1980 that completely transformed US politics!
Politics at a national level looks very, very similar nationwide. Rural areas in Vermont look like rural areas in Montana look like rural areas in KY, as far as voting patterns go. (Same w/ cities.)
The biggest effect of Reagan was that Democrats jolted to the right to catch up. I don't think somebody like Edwin Edwards could have run after Reagan left office, because that kind of advocacy for the poor was no longer in the Democrats' playbook. Remember that Bill Clinton spent part of his presidency gutting welfare on the advice of a white supremacist.
Policies that specifically target working class voters, irrespective of race, could do a lot to flip Southern seats in congress, particularly in poorer districts with substantial minority populations.